<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    *{
      padding: 0;
      margin: 0;
    }
    .row{
      display: flex;
      width: 1000px;
      justify-content: space-evenly;
      margin-bottom: 15px;
    }
    .row>div{
      width: 300px;
      height: 150px;
      background: #000;
    }
  </style>
</head>
<body>
  <div class="main">
    <div class="row">
      <div>单独商品</div>
      <div>单独商品</div>
      <div>单独商品</div>
    </div>
    <div class="row">
      <div>单独商品</div>
      <div>单独商品</div>
      <div>单独商品</div>
    </div>
    <div class="row">
      <div>单独商品</div>
      <div>单独商品</div>
      <div>单独商品</div>
    </div>
    <div class="row">
      <div>单独商品</div>
      <div>单独商品</div>
      <div>单独商品</div>
    </div>
  </div>
</body>
</html>